1. Field of the Invention
The present invention relates to implanting devices for implanting pellets or the like, e.g. growth promotant implants, subcutaneously or intramuscularly in animals. In particular, the present invention relates to those devices having a retractable needle and a mechanism for sequencing an implant magazine having a plurality of pellet-containing stations therein for sequential administration of the implant doses. Additionally, the invention relates to an implant magazine having a plurality of pellet-containing stations therein which has means for facilitating the ejection of pellets from the implant magazine and substantially eliminating or preventing breakage and crushing of the implant pellets.
2. State of the Art
Numerous implanting instruments have been described in the art. The following patents are considered representative examples thereof: U.S. Pat. Nos. 2,632,444; 2,883,984; 3,058,465; 3,088,207; 3,402,712; 3,520,299; 3,538,916; 3,669,104; 4,077,406; 4,105,030; 4,154,239; 3,774,607; 4,223,674; Canadian Pat. No. 455,838; and Australian Pat. Nos. 223,184; 228,022; 253,175; and 288,070. Additional patents relating to implant cartridges and other magazines generally are U.S. Pat. Nos. 202,613; 1,559,825; 2,493,922; 2,587,687; 2,601,852; 3,477,419; 3,913,553; and 3,729,853.
Many implant dosage forms are relatively fragile and have a tendency to break or crush when forced out from the implant magazine into and through the needle into animal tissue. Relatively recently, devices having a retractable needle which obviates the necessity of pushing pellets from the implanter into the tissue have been developed. For example, U.S. Pat. Nos. 4,223,674 (Fluent et al) and 4,105,030 (Kercso) have described devices having a retractable needle which is drawn rearwardly from about the implant pellets to permit the pellets to remain in the animal tissue. However, there remains the problem of expelling the implant pellets from the implant magazine itself into the needle. During that step of the implanting procedure, there is a tendency for pellets to break or crush. Additionally, it is not generally desirable to have the implant pellets freely moveable within the pellet containing stations of the implant cartridge since there is a tendency for the pellets to drop out during handling of the implant magazine such as, for example, when the implant magazine would be loaded into the implanting device. Furthermore, each of those devices utilizes a multidose magazine which requires manual indexing of the implant magazine for each sequential application of an implant to an animal. Such manual indexing is unsatisfactory in many applications such as feedlot usage where large numbers of animals are implanted during one operation. Additionally, failure to manually index the cartridge prior to implantation would result in a false implant. Accordingly, there is a need for automatically indexing the cartridge prior to the sequential injection of subsequent animals.